Process of extracting precious metals from ores containing alkaline-earth carbonates, &amp;c.



" "llmilm tMm Mar Eur orrrbl fii m n s. inseam AND DONALD B. BRALDNER, or roNoram nvnnap r noonss or EXTNACTI G' rnncrocsivrnrnLs rnor/i onns CONTAINING ALKALINE- EARTH CARBONATES, 8w. a

inertia.

No Drawing.

To all wlwm'it may concern:

Be it known that We, JOHN KmonnN and DONALD B. BRADNER, citizens of the United States, residing at Tonopalnin the county of Nye and State of Nevada, have invented certain newand useful Improvements in Processes of Extracting Precious Metals from Ores Containing Alkaline Earth Carbonates, 850., of which the following is a specification.

This invention relates to a process of treating gold or silver ores carrying calcite, limestone, or any alkaline earth carbonates.

A certain class of ores found in the Manhattan district of Nevada have been prac tically valueless since their discovery, owing to the presence of antimony, arsenical compounds and certain carbonates. It has not hertofore been found possible to reduce these ores and the entire district in which these ores are found, instead of progressing and growing up as a prosperous mining community has become depressed and almost depopulated.

The general object of. this invention is to provide a method whereby these ores may be reduced and treated by the cyanid process to secure the precious metals therefrom, and particularly to provide a process whereby the precious metals may be removed from the ore but at such a temperature that limestone, calcite and other alkaline earth carbonates, which are contained in the ores, will not be decomposed by the liberation of carbon dioxid and will therefore remain in soluble in water or cyanid solution.

The process is as follows: The ores which are to be treated are ores carrying gold and silver, stibnite or antimony sulfid, calcite, calcium carbonate and other alkaline earth carbonates. This ore is roasted at a relatively low temperature to free the precious metals in the ore, the temperature being sufliciently high that the sulfids of arsenic and iron are oxidized and part of the sulfid of antimony oxidized but being so low that the limestone, calcite, and the alkaline earth A carbonates shall not be decomposed by the liberation of carbon dioxid and will there fore remain insoluble in water or cyanid solution.

We have found by careful experiment that the roasting at a temperature not less than 600 F. approximately and not higher than 1200 F. or preferably not higher than 1150 Specification Orlean n n.

Patented n t. as, late. Application filed August a, 1917. it ser al fio. 185,189. l

F. "will notcause the liberation of carbon:

dioxid, but will eliminate the"volatile ;hy I

drecarbons from any carbonaceous material that may be contained in the ore and that ifthe roasting temperature is carried over 1150 or 1200 F., caustic lime will be formed which, in the subsequent cyanid treatment, dissolves the partially oxidized antimony ,sulfid and causes preclpitation of the gold. In other words, if the roasting temperature is carried above 1150 F. or 1200 F.,the carbon dioxid is liberated from the limestone, calcite, etc, leaving the residue of the limestone, calcite, antimony sulfid, etc., in a soluble condition and, therefore, in a condition to combine with the gold and silver.

The roasting of the ore at a temperature below 1200 F. frees the precious metals from the ore. That is, in the case of sulfids of iron and arsenic, oxidization vola tilizes the sulfur so that the old contained within the sulfids is freed. f coursegold exists in other combinations than with the sulfid minerals, but we have found that roasting between 600 'F. and 1200 F. breaks up the combination of gold with other non-.. sulfid minerals, liberating the gold there from and making it free, so that the gold contained in the original arsenic sulfids, iron sulfids or in combination with non-sulfid minerals is placed in a free state so that it is readily soluble in a cyanid solution. Very often graphitic material is contained in the ore and this roasting expels the volatile hydro-carbons which may be contained in the graphitic material.

The process may be applied to the treatment of metallic ores carrying limestone, calcite or other alkaline earth carbonates with antimony sulfid, realgar, orpiment, or other arsenical sulfids, etc., or with non-sulfid minerals, so that the alkaline earth carbonates which are naturally practically insoluble, remain insoluble.

Having described our invention, what we claim is 1. A step in the process of extracting precious metals from ores containing calprecious metals frdih ores 'coht'a'iiii'ng calcium carbonate, and ether alkaline earth carbonatesficcfieiting in resistingthe Ore at .a temperature greater than 600 F but less tharr-1200 3. Theprocess of extracting preci'tcus hretals frqm ores containing calcium carbonate,

ing in roasting the ore at ,atemperature greater than 600 F. but lees than that which will liberate carbondi'oXid" and then submittingthe calcinerto a cyanid treatment.

lgg-A gtepin the process oftreating; ores includingcprecious meta1S, -'ea-rth carbonates,

Witnesses:

B. W; Boc'm, Arne M. CASE.

bailey.hiy fieiehtainiir foray; cent; each,- byhdliiefiing-theCommissioner of Patentm v r Washmgton,.D. 0'.," 

